Heat exchanger for dryer and condensing type dryer using the same

ABSTRACT

A heat exchanger for a dryer includes a plurality of tubes for circulating wet air and a plurality of fin structures for circulating external air which are alternately laminated together to form the heat exchanger. The fin structure includes a plurality of air passages formed by repeatedly bending a flat-type metal plate in a zigzag form. A plurality of fins are formed on side surfaces of the air passages. The fins protrude from the side surfaces of the air passages at an inclination angle. The fins are formed by partially cutting the plate forming the side surfaces of the air passages, and by the bending the cut portions of the plate into the air passages to from the fins. A heat transfer area and a heat transfer efficiency are increased, thereby enhancing a drying efficiency of a dryer having the heat exchanger.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger for a condensing typeDryer.

2. Description of the Background Art

A laundry or clothes dryer serves to dry an object to be dried byblowing hot air generated from a heater into a drum. The dryers aredivided into an exhausting type and a condensing type, according to amethod for processing the humid air generated as the object to be driedis dried.

In the exhausting type dryer, humid air exhausted from a drum isexhausted outside the dryer. In the condensing type dryer, humid airexhausted from a drum is condensed by a condenser, to remove moisturefrom the air, and the dry air is fed back into the drum to bere-circulated.

The condensing type dryer comprises a drum for drying laundry, a filterfor filtering foreign materials, a heat exchanger (or condenser) forremoving moisture, a fan, a heater for shortening the drying time, andpiping or ducts for connecting each component. One example of acondensing type dryer is shown in FIGS. 1A and 1B. In FIGS. 1A and 1B,the single line arrows denote a flow of external air, and the doubleline arrows denote a flow of air that is re-circulated through the drumof the dryer and the heat exchanger/condenser.

As shown, a drum 11 for receiving an object to be dried is rotatablyinstalled in a body 10 having a door 12 at a front surface thereof. Thedrum 11 is connected to a motor 17 installed at a lower portion of thebody 10 by a belt 19 which serves to rotate the drum 11. A condenser 13for condensing hot humid air that has passed through the drum of thedryer, thereby removing moisture from the air, is installed at a lowerportion of the body 10. A front portion and a rear portion of thecondenser 13 are respectively connected to a circulation duct 14, whichitself is connected to front and rear sides of the drum 11. This allowsair to be exhausted from the drum and into the condenser 13, and the aircan then be re-introduced to the drum 11.

The circulation duct 14 is provided with a heater 15 for heating airthat has passed through the condenser 13 and a circulation fan 16 forforcibly circulating the air. The circulation fan 16 is connected to ashaft of the motor 17. Reference numeral 22 denotes a filter forfiltering foreign materials such as lint, etc. from air exhausted to thecirculation duct 14 through the front side of the drum 11.

In order to condense air circulated by the circulation duct 14 in thecondenser 13, external cold air has to be supplied to the condenser 13.Accordingly, an external air supplying duct 18 connected to outside ofthe body 10 is connected to one side of the condenser 13. A cooling fan20 and a cooling fan driving motor 21 for forcibly sucking external airthrough the external air supplying duct 18 and then exhausting the airinto the body 10 are connected to another side of the condenser 13. Awater collector (not shown) for collecting condensing water generated atthe time of a condensing process is installed at a lower portion of thecondenser 13. Also, a pump 23 for transmitting the condensing watercollected in the water collector to a condensing water storage tank 2 isinstalled at a lower portion of the condenser 13.

One example of the heat exchanger used for a condensing type clothesdryer is shown in FIG. 2. As shown, dry air introduced into an externalair inlet 13 a is heat-exchanged with wet air introduced into a wet airinlet 13 b inside the heat exchanger. During the heat exchange process,the wet air is condensed onto a surface inside the heat exchanger andthus water drops are generated.

One would like to be able to dry laundry with less consumption of powerwithin a shorter period of time. In order to shorten drying time, aheater capacity or a fan capacity has to be increased. However, thesechanges usually cause a cost increase, an electricity charge increase,or a noise increase.

BRIEF DESCRIPTION OF THE INVENTION

In the condensing type dryer, the heat exchanger is a core componentthat influences a drying efficiency. A heat exchanger that provides agreater heat transfer efficiency would allow the dryer itself to be moreefficient, without increasing the power consumption.

Therefore, an object of the present invention is to provide a heatexchanger having a new structure capable of enhancing a heat transferarea and a heat exchanging efficiency.

Another object of the present invention is to provide a heat exchangercapable of reducing a fabrication cost and enhancing productivity.

Still another object of the present invention is to provide a heatexchanger for a dryer capable of enhancing an efficiency of the heatexchanger and thereby enhancing an efficiency of the dryer.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, aheat exchanger for a dryer embodying the invention includes a pluralityof tubes/ducts for circulating wet air and a plurality of air passageswith fin structures for circulating external air. The ducts and airpassages are stacked, one on top of another in an alternating fashion toform the heat exchanger. The fin structure and of air passages areformed by repeatedly bending a flat-type metal plate in a zigzagfashion. A plurality of fins are formed on sidewalls of the airpassages. The fins may protrude from the sidewalls into the air passagesat an inclination angle. The plurality of fins formed on each sidewallsurface of the air passages are divided into two groups, each of whichhave a different inclination angle.

A condensing type dryer embodying the invention includes a drumrotatably installed in a cabinet; a heat exchanger/condenser forheat-exchanging wet air with air introduced from outside and therebycondensing the wet air; a fan; and a heat source for heating the aircirculating in the dryer. The heat exchanger/condenser would beconstructed as described above.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1A is a sectional view showing one example of a clothes dryer;

FIG. 1B is a plane view showing the clothes dryer of FIG. 1A;

FIG. 2 is a perspective view showing one example of a heatexchanger/condenser;

FIG. 3 is an exploded view showing components of a heat exchangeraccording to the present invention;

FIG. 4 is a perspective view showing a laminated structure of a heatexchanging portion of the heat exchanger according to the presentinvention;

FIGS. 5A to 5C are diagrams showing details of a fin structure of a heatexchanger/condenser according to the present invention;

FIG. 6 is a photo showing the fin structure of a heatexchanger/condenser according to the present invention; and

FIG. 7 is a graph showing a heat transfer performance of a heatexchanger/condenser according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

A heat exchanger according to the present invention enhances anefficiency thereof by increasing a heat transfer area. Heat transfer canbe smoothly performed between wet air circulated in a dryer and airintroduced from outside of the dryer. Heat exchange is also increased byintroducing external air into the heat exchanger as a turbulent flow. Inan experiment for heat exchange performance, a heat exchanger embodyingthe present invention showed an efficiency that was more than 15%greater than comparable prior art designs.

In FIG. 3, components of a heat exchanger according to the presentinvention are shown. A heat exchanger 30 is formed as a plurality oftubes 32 and a plurality of fin structures 34, which are stackedtogether in an alternating fashion. Each of the tubes 32 has a ductstructure in which both ends are open. A cross-section of the tubes 32has a rectangular shape. A pipe or duct (not shown), along whichcirculating air from inside the dryer flows, is respectively connectedto the opened ends of the tubes 32. The fin structures 34 comprise aflat plate that has been repeatedly bent in a zigzag form.

The tubes 32 and the fin structures 34, each having a thin thickness,are stacked on one another to form a heat exchanger. The more tubes 32and fin structures 34 that are added, the more the heat transfer areacan be increased. FIG. 4 shows a process for laminating each tube 32 andeach fin structure 34.

The tube 32 and the fin structure 34 are both formed of a metal havingan excellent heat transfer characteristic, such as Al or Al alloy. Afront cover 40 and a rear cover 42 are respectively coupled to a frontsurface and a rear surface of the heat exchange portion 30. The frontcover 40 and the rear cover 42 couple the heat exchange portion 30 tothe pipes, ducts or other components inside the dryer. The front cover40 and the rear cover 42 are preferably formed of a plastic basedmaterial such as ABS-GF by an injection molding. A sealing member forpreventing air leakage can be formed at both ends of the heat exchangeportion 30 to which the front cover 40 and the rear cover 42 arecoupled.

The fin structure 34 is preferably formed as a rectangularparallelepiped shape having a constant thickness, width, and length bybending a metal plate in a zigzag form. As the metal plate is bent in azigzag form, a structure having repeatedly formed valleys is formed. Thetubes 32 are then adhered to upper and lower surfaces of the structure.The spaces between the flat parallel portions of the bent plate form airpassages into which external air is introduced and then is exhaustedtherefrom after a heat exchange.

A plurality of fins are formed on the flat parallel sidewalls of the airpassages. The fins are formed on at least one side of each air passage,and preferably on both sides of each air passage. The plural fins areactually portions of the flat sides of the plate that have been cut andthen bent inward into the air passages. The fins protrude from thesurfaces of the air passages at an inclined angle.

The fin structures 34 are formed by partially cutting the metal plateand then repeatedly bending the metal plate in a zigzag form so as toform a plurality of air passages. The process can be performed by oneconsecutive processing using an automatic machine.

The fin structure 34 of the heat exchanger according to the presentinvention is shown in FIGS. 5A to 5C, which are views as seen from thedirections of arrows A, B, and C of FIG. 4. A plurality of fins 36 areformed on the sidewall surfaces of the air passages 37. The fins 36 areprotruding from the opposing flat parallel surfaces of the air passages37 at an inclined angle. The fins 36 have a shape corresponding toscales of fish, and serve as a medium for contacting external airintroduced into the heat exchanger and transferring heat into or awayfrom the passing through the air passages.

The fin structure 34 of the heat exchanger according to the presentinvention is easily fabricated since the plural fins 36 are formed tohave a simple structure. For instance, the fins 36 can be protrudingfrom the surface of the metal by partially cutting the surface of themetal on the air passage 37 by punching or by other means.

The plural fins 36 are divided into two groups, each of which are bentin different directions on one surface of the air passage. External airflowing through the air passages performs a heat exchange with wet airinside the dryer that is circulating through the tubes 32. In order toeffectively perform the heat transfer, the external air preferably formsa turbulent flow because of the fin structure. The plural fins on thesurfaces of the air passage are bent in different directions to promotea turbulent flow. The turbulent flow facilitates external air thatpasses through the air passage of the fin structure to obtain heat fromthe high temperature wet air passing through the tubes 32. Two fingroups 36 a and 36 b having different inclination directions are shownin FIGS. 5B and 5C. FIG. 6 shows a photo of a completed fin structure.

In the heat exchanger according to the present invention, the finstructure influences the heat exchange performance. For example, thefins 36 preferably protrude from the sidewalls of the air passages 37 byapproximately 0.4 to 0.7 mm. If the protruding portions of the fins 36are too small, external air is not in good contact with the fins. On theother hand, if the protruding portions of the fins 36 are too large,flow friction of the external air is increased and thus noise isincreased.

A gap between the fins is formed to be 1 to 3 mm, preferably, to be 1.5to 2.5 mm. If the gap is too small, flow friction of external air isincreased. On the other hand, if the gap is too great, a heat transferis decreased.

A thickness of the fin structure 34 is determined by considering arelationship with the tube 32 coupled to the fin structure 34. Thethickness of the fin structure 34 can vary, but preferably has a rangeof 8 to 10 mm. The thickness of the tube is preferably thinner than thethickness of the fin structure in order to enhance heat transfer.

A distance between the surfaces of each air passage 37 in the bent finstructure 34, that is, a pitch of the fin structure, is formed not to betoo small or too large. If the pitch is too large, heat exchange islowered and thus heat transfer efficiency is degraded. On the otherhand, when the pitch is too small, external air has a large flowresistance, which increases noise even when heat exchange is increased.In the heat exchanger according to the present invention, the finstructure preferably has a pitch corresponding to 3 to 6 mm.

FIG. 7 shows the results of a heat transfer performance test, whichmeasured a heat transfer characteristic for several different heatexchangers. In FIG. 7, the first result is for a prior art heatexchanger having an offset fin structure which is different from thepresent invention. The second and third results are for a heat exchangerembodying the invention, wherein the pitch of the air passages was setto be 4 mm and 5 mm, respectively.

The heat transfer characteristic was calculated by the followingformula.Q=m·c _(p) ·ΔT (dried state)Q=m·Δh (wet state)

In the above formula, the heat transfer characteristic, that is, a heatquantity variation (Q) is obtained by multiplying a mass (m) of flowingair, a constant pressure specific heat (c_(p)), and a temperaturevariation (ΔT) to one another in a dried state. Also, the heat transfercharacteristic is obtained by multiplying a mass (m) of flowing air andan enthalpy variation amount (Δh) to each other in a wet state.

From the result, it is clear that a heat exchange performance becomesdifferent when the pitch of the air passage becomes different. Also,when compared with a heat exchanger having an offset fin structure, theheat exchangers having a fin structure according to the presentinvention have a heat exchange performance that is increased by as muchas 15%.

As aforementioned, in the present invention, a heat transfer area and aheat transfer amount are increased, to thereby enhance an efficiency ofthe heat exchanger. The heat exchanger is used in a dryer as part of acondenser to remove water from the air being circulated through thedryer. This increases a drying efficiency of the dryer. Furthermore,since a fabrication cost of the heat exchanger is reduced, a price ofthe dryer is lowered and thus a product competitiveness is enhanced.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims. All changes andmodifications that fall within the metes and bounds of the claims, orequivalence of such metes and bounds are therefore intended to beembraced by the appended claims.

1. A heat exchanger, comprising: a plurality of first ducts forconveying a first fluid flow; and a plurality of second ducts forconveying a second fluid flow, wherein the plurality of first ducts andthe plurality of second ducts are stacked upon one another in analternating fashion, and wherein each of the plurality of second ductscomprises: a plurality of air passages formed by repeatedly bending aflat plate in a zig-zag fashion such that the plate forms opposingsidewalls; and a plurality of fins that protrude from the opposingsidewalls of the air passages, wherein the fins comprise portions of theplate that are bent so that they extend into the air passages.
 2. Theheat exchanger of claim 1, wherein the fins are formed by selectivelycutting portions of the plate that forms the plurality of air passages,and then bending the cut portions so that they form fins that extendinto the air passages at an inclination angle relative to the sidewalls.3. The heat exchanger of claim 2, wherein the fins on each sidewall aredivided into two groups, wherein the fins in the first group extend intothe corresponding air passage at a first inclination angle, and whereinthe fins in the second group extend into the corresponding air passageat a second inclination angle.
 4. The heat exchanger of claim 3, whereinthe first group of fins are grouped together along a first portion ofthe air passage, and the second group of fins are grouped together alonga second portion of the air passage.
 5. The heat exchanger of claim 4,wherein the first group of fins and the second group of fins extendtowards one another.
 6. The heat exchanger of claim 2, wherein fins areformed on both sides of the majority of the sidewalls of the airpassages.
 7. The heat exchanger of claim 1, wherein the plurality offirst air ducts extend in a first direction, and wherein the pluralityof second air ducts extend in a second direction that is orientedapproximately perpendicular to the first direction.
 8. The heatexchanger of claim 1, wherein the heat exchanger is configured to beused in a clothing dryer, wherein the plurality of first air ducts areconfigured to convey a flow of heated air that is recirculated through adrum of the dryer, and wherein the plurality of second air ducts areconfigured to convey a flow of air from outside the dryer.
 9. The heatexchanger of claim 8, wherein the heat exchanger is configured to coolthe flow of heated air in the plurality of first air ducts to condensefluid in the heated air.
 10. The heat exchanger of claim 1, wherein theplurality of fins have a height of approximately 8-10 mm.
 11. The heatexchanger of claim 1, wherein a pitch between the air passages in eachof the second air ducts is approximately 3-6 mm.
 12. The heat exchangerof claim 1, wherein the fins protrude into the air passagesapproximately 0.4-0.7 mm.
 13. The heat exchanger of claim 1, wherein agap between fins on opposing sidewalls of the air passages isapproximately 1-3 mm.
 14. The heat exchanger of claim 1, wherein theplurality of first ducts have a rectangular cross-sectional shape.
 15. Aclothing dryer comprising the heat exchanger of claim
 1. 16. A heatexchanger, comprising: a first duct for conveying a first fluid flow;and a second duct for conveying a second fluid flow, wherein the firstduct and the second duct are stacked upon one another, and wherein thesecond duct comprises: a plurality of separate air passages havingopposing sidewalls; and a plurality of fins that protrude from theopposing sidewalls of the air passages, wherein the fins compriseportions of the sidewalls that are bent so that they extend into the airpassages.
 17. The heat exchanger of claim 16, wherein the fins areformed by selectively cutting portions of the sidewalls of the airpassages, and then bending the cut portions so that they form fins thatextend into the air passages at an inclination angle relative to thesidewalls.
 18. The heat exchanger of claim 17, wherein a plurality offirst air ducts and a plurality of second air ducts are stacked upon oneanother in an alternating fashion to form the heat exchanger.
 19. Theheat exchanger of claim 17, wherein the fins on each sidewall aredivided into two groups, wherein the fins in the first group extend intothe corresponding air passage at a first inclination angle, and whereinthe fins in the second group extend into the corresponding air passageat a second inclination angle.
 20. The heat exchanger of claim 19,wherein the first group of fins are grouped together along a firstportion of the air passage, and the second group of fins are groupedtogether along a second portion of the air passage.